Vehicles incorporating electric motors as their driving sources are known, such as hybrid vehicles, electric vehicles, and fuel cell vehicles. Each of such vehicles is provided with a battery for storing electric power to be supplied to the electric motor. Some of the vehicles are configured to be capable of charging the battery with electric power supplied from a power supply external to the vehicle. Hereinafter, a vehicle capable of charging the battery with electric power supplied from a power supply external to the vehicle is also referred to as a plug-in vehicle. Electric power is supplied to a battery mounted on a plug-in vehicle via a charging cable connected to the plug-in vehicle, a power line disposed in the plug-in vehicle, and the like.
A well known technology relating to PLC (Power Line Communication) makes it possible to utilize a charging cable and a power line as a communication path. Generally, PLC is capable of sending and receiving data faster than wireless communication. Therefore, a fast transmission of data for use in, for example, a car navigation system for a plug-in vehicle can be achieved by PLC utilizing a charging cable and a power line, instead of wireless communication utilizing a cell phone or the like.
A variety of equipment such as an inverter serving as a charger, for example, is connected to a power line, and therefore, noise could superimpose on a power line. Thus, to enhance the communication quality of PLC, some communication apparatuses using PLC are provided with the function of filtering as described in paragraph 72 of Japanese Patent Laying-Open No. 2007-236173 (PTL 1).